The invention relates to a labeling machine for objects, and more particularly for bottles, which comprises conveying means for the objects; a revolving carrier having at least one label pickup member mounted thereon to rotate or oscillate; and stations disposed about said carrier, these being a gluing station, a label supply station and a label transfer station with which the pickup member or members cooperate, the gluing station consisting of a revolving glue roll, a deactivatable glue applicator, and an engageable glue scraper.
A labeling machine of this type is known from Application Ser. No. 72,378, filed Sept. 4, 1979, now U.S. Pat. No. 4,279,687. In that labeling machine a second glue scraper is provided which permits the thickness of the glue layer to be adjusted. However, that glue scraper is mounted along with the glue applicator on a pivotable carrier. An angular displacement of the carrier causes the glue applicator, constructed as a slot nozzle, to be moved away from the glue-roll surface, the application of glue thus being interrupted; and that same displacement also serves to position the glue scraper so that it bears tangentially on the glue roll. The function of the glue scraper then is to scrape off the glue still on the roll. Since the pickup members continue to roll along the glue-roll surface, they retransfer glue to the glue-roll surface, which means that the pickup members, too, may indirectly be freed of glue in this way.
However, it has been found that scraping the glue-roll surface completely dry, and allowing the pickup surfaces of the pickup members to dry completely, has certain disadvantages. While the major drawback of the machine being fouled by glue that is thrown off is then overcome, there is no preventing the edges of the pickup surfaces of the pickup members from becoming encrusted with drying glue, with the result that the pickup surfaces are enlarged, glue then being transferred also to areas on the objects being labeled where it is not needed and where it is an eyesore. Besides, with completely dry surfaces there will be more friction and hence increased wear.
A remedy resorted to in practice has been to cover the machine with moist towels during interruptions of operation, such as breaks, in order to minimize surface drying, and/or to clean the machine at the end of the break. But this is a primitive and onerous way of keeping the machine ready for use.
A further problem encountered in operating that labeling machine is that after an extended interruption of operation, for example, when starting work in the morning, the cold pickup members will not readily pick up the warm glue from the glue roll, and the labels carried by the pickup members are not readily picked off by the gripper cylinder. This means that the machine cannot be brought up to speed right away. But optimum glue-handling conditions are important also during operation. When the atmosphere is too dry or the pickup members are too warm or too cold, then the glue, which may be casein-based, for example, will set prematurely, depending on its grade (casein glue, for example, or dextrin glue), so that in the course of time a glue layer builds up on the pickup members that becomes steadily thicker. This will result in imprecise application of glue to the pickup members, which will have an adverse effect on the pickup of labels from the label stack.